//
// Created by WuShiHai on 26/11/2016.
//

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <sys/socket.h>

#define BUF_SIZE 1024
#define OPSZ 4

void error_handling(char *message);
int calculate(int opnum, int opnds[], char operator);

int main(int argc,char *argv[]){
    int serv_sock,clnt_sock;
    char opinfo[BUF_SIZE];
    int result,opnd_cnt,i;
    int recv_cnt, recv_len;
    struct sockaddr_in serv_adr, clnt_adr;
    socklen_t clnt_adr_sz;

    if (argc != 2){
        printf("Usage : %s <port>\n", argv[0]);
        exit(1);
    }

    serv_sock = socket(PF_INET,SOCK_STREAM, 0);
    if (serv_sock == -1){
        error_handling("socket() error!");
    }

    memset(&serv_adr,0, sizeof(serv_adr));
    serv_adr.sin_family = AF_INET;
    serv_adr.sin_addr.s_addr = htonl(INADDR_ANY);
    serv_adr.sin_port = htons(atoi(argv[1]));

    if (bind(serv_sock,(struct sockaddr*)&serv_adr, sizeof(serv_adr)) == -1){
        error_handling("bind() error!");
    }
    if (listen(serv_sock, 5) == -1){
        error_handling("listen() error!");
    }

    clnt_adr_sz = sizeof(clnt_adr);
    for (int i = 0; i < 5; ++i) {
        opnd_cnt = 0;
        clnt_sock = accept(serv_sock, (struct sockaddr*)&clnt_adr, &clnt_adr_sz);
        read(clnt_sock,&opnd_cnt,1);

        recv_len = 0;
        while ((opnd_cnt * OPSZ + 1) > recv_len){
            recv_cnt = read(clnt_sock, &opinfo[recv_len],BUF_SIZE - 1);
            recv_len += recv_cnt;
        }

        result = calculate(opnd_cnt, (int *)opinfo, opinfo[recv_len - 1]);
        write(clnt_sock, (char *)&result, sizeof(result));
        close(clnt_sock);
    }
    close(serv_sock);
    return EXIT_SUCCESS;
}

int calculate(int opnum, int opnds[], char op){
    int result = opnds[0],i;
    switch(op){
        case '+':
            for (int i = 1; i < opnum; ++i) {
                result += opnds[i];
            }
            break;
        case '-':
            for (int i = 1; i < opnum; ++i) {
                result -= opnds[i];
            }
            break;
        case '*':
            for (int i = 1; i < opnum; ++i) {
                result *= opnds[i];
            }
            break;
    }

    return result;
}

void  error_handling(char *message){
    fputs(message, stderr);
    fputc('\n',stderr);
    exit(1);
}